Threaded component for seizure-resistant tubular threaded joint

ABSTRACT

The invention concerns a threaded component for a seizure-resistant tubular threaded joint wherein a lubricating substance is deposited in a thin film on at least the surface of the threads of the threading, said surface being treated to adsorb said lubricating substance. The lubricating substance consists of a homogeneous mixture of a) a thickening agent; b) a set of extreme-pressure additives physically and chemically compatible with the thickening agent and comprising at least an extreme-pressure additive with chemical action called chemical EP additive and capable of being used at Hertz pressures not less than 1000 Mpa&#39;s; c) an oil. The proportions of the constituents of the lubricating substance are selected such that said lubricating substance has a consistency capable of ensuring a self-induced and film-forming lubricating process. The invention also concerns a method for producing the thin film.

The present invention relates to male or female elements disposed at theend of pipes and intended to be connected by making up to constitutegalling-resistant threaded tubular connections and more particularlythose intended for making up without the manual addition of grease.

Such threaded elements and threaded tubular connections are known to beused in particular to constitute casing strings or production strings ordrillpipe strings for hydrocarbon wells or the like, such as forinstance geothermal wells.

Such types of pipes are generally made up vertically, the free end ofthe string at the surface comprising a female threaded element with aninternal female threading.

In order to lower the string into the well, a new pipe is provided abovethe string provided with a male threaded element comprising an externalmale threading corresponding to the female threading at thecorresponding free end of the string, the male threading of the new pipeis engaged in the corresponding female threading of the string and thenew pipe is made up until the makeup torque reaches a given value or agiven reference. The string can then be lowered by the length of thepipe that has been connected and the process is repeated.

Because of the length of the pipes, about 10 m, it is not easy to engagethe new pipe perfectly co-axially with the top of the string. Thus, thethreadings suffer enormously during connection and more particularly,the stabbing flanks of the male and female threads which rest againsteach other during engagement and are in sliding contact for a largeproportion of makeup. The stabbing flanks of the threads are thus highlysensitive to the phenomenon of galling that can occur, if not during thefirst makeup at least during the subsequent makeup procedures, athreaded tubular connection having to be capable of being made up andbroken out many times without galling.

Galling can also occur at “metal-metal” sealing surfaces present on thethreaded elements of the threaded tubular connections known as “premium”connections, such sealing surfaces being in sliding contact underincreasing contact pressure up to the final makeup position.

This is also the case for the abutment surfaces, which come into contactat the end of makeup.

Therefore it is out of the question to constitute purely metal-metalsliding contact surfaces both for the threadings and for the sealingsurfaces or the abutments if the threaded connection is providedtherewith, since the constitution of such surfaces would inevitablycause galling, which is unacceptable.

The conventional solution, which has been employed for many years, is tointerpose a grease between the metallic surfaces that are in slidingcontact, that grease being applied to the threaded element in batches.

The most widely used grease is API type 5A2 or 5A3 grease specified bythe American Petroleum Institute (API) which is a heterogeneous mixtureof a grease, graphite particles and Pb, Zn and Cu metals which has bothanti-galling properties and fills the clearance between the male andfemale threads.

Such a grease, however, suffers from a number of disadvantages.

The first disadvantage of API grease linked to its nature is its amountin lead, an element that is particularly noxious to health and to theenvironment.

Such a grease also has other disadvantages, some of which are common toall greases.

Because of those characteristics, the grease is generally applied with abrush to the contact surfaces of the threaded elements. Care is takenthat a minimum quantity of grease, measured by a minimum volume orminimum mass, is applied to the surfaces: thus Vallourec Mannesmann Oil& Gas France, in its booklet “VAM® Running Book”, produced by thecompany in July 1996 for its clients, specifies a volume of at least 25cm³ or a mass of at least 42 g of API Bul 5A2 grease to coat the contactsurfaces of male and female elements of VAM® TOP threaded connectionswith a 7″ (177.8 mm) external diameter.

This results in a certain variability in the quantities of greaseapplied to the threaded elements:

-   -   a) According to the operators in charge of the grease coating        operation, in particular on site;    -   b) for the same operator, from one threaded element to another;        and    -   c) for the same threaded element, from one point on the threaded        element to another.

The makeup operation distributes the grease in the clearances betweenthe male threads and corresponding female threads, these clearancesvarying in a random manner from one threaded connection to another dueto the manufacturing tolerances for the threaded elements, and leads toejection of surplus grease from the threaded connection.

For certain types of threaded connections, the difficulty in evacuatingsurplus grease may result in the production of very high pressures onthe threads during makeup that may alter the measurement of the makeuptorque, or even deform the threads and the sealing surfaces, even withtapered threadings (recommended by the API and thus widely used) andlead in the event of excessive application to the threadings jumpingout, with a catastrophic drop of the string to the bottom of the well.

In addition, surplus grease ejected during makeup accumulates at thebottom of the well in large amounts taking into account the number ofthreaded connections used, and block the pores of the reservoir rock,which pores must be traversed by the hydrocarbons before being recoveredby the production pipes. Such a blocking considerably affects theexploitation costs of hydrocarbon wells.

Further still, certain greases, including API 5A2 or 5A3, do not offersufficient anticorrosion protection because of their composition and theconditions and duration of transport and/or storage of the pipes beforeuse.

It may then be necessary at the manufacturing factory to apply a greasethat is specific for transport and storage to the contact surfaces ofthe threaded elements, then to eliminate it on site just beforeconnecting the pipes and then to apply a final API 5A2 type grease formakeup.

A number of other types of grease, with or without lead, have beendescribed in patents concerning threaded connections.

Such greases are often heterogeneous, being charged with metallicparticles, mineral particles or thermoplastic particles to fill theclearances between the male and female threads (GB 1 086 720, U.S. Pat.No. 3,526,593) and/or to prevent galling during makeup (U.S. Pat. Nos.2,065,247, 5,275,845) or on breakout (GB 1 033 735, U.S. Pat. No.2,419,144).

The anti-galling properties of certain of the greases described in thosepatents may result from the presence of extreme pressure additives inthose greases, which act chemically: U.S. Pat. Nos. 2,065,247,3,095,375.

However, those patents concern greases which as a result possess thedisadvantages of all of the greases indicated above for API 5A2 or 5A3greases.

Coatings with a solid consistency applied by the pipe manufacturer tothe threads and bearing surfaces were then developed, enabling “dry”makeup of threaded connections without the need for subsequentapplication of lubricant on site.

Such coatings may be metallic in nature, such as those described inEuropean patent EP 632 225, which employ an external layer of lead, orbased on metallic oxides such as those described in EP 500 482, whichemploy an external layer of lead oxide, however those coatings involvethe undesirable presence of lead or lead compounds.

Such coatings can also be a paint or a sliding varnish.

Patent application EP 786 616 describes a method for producing such asliding varnish on a threaded element, which method comprises priordeposit of a thin layer (0.005 to 0.030 mm) of phosphate then a 0.010 to0.045 mm thick layer of a mixture of an epoxy type synthetic resin or ofanother type and molybdenum disulfide or tungsten disulfide andpolymerizing the resin by heating.

U.S. Pat. No. 4,414,247 also describes a similar method for producing asliding varnish on a threaded element.

Such sliding varnishes have excellent anti-galling properties as long asthey are present. However as solid varnishes, they wear and are notregenerated during repeated makeup-breakout operations. Thus, afterseveral makeup-breakout operations galling is observed on threadedconnections provided with such coatings, said galling being then suddenand catastrophic.

Further, if such a sliding varnish becomes locally deteriorated duringpipe transport or storage, the varnish layer cannot be repaired locally.

The present invention seeks to obtain a male or female threaded elementfor a threaded tubular connection that is particularly resistant togalling, comprising a male or female threading depending on the type ofthreaded element which, being provided with a lubricating layer on thesurfaces intended to become contact surfaces, is free of thedisadvantages cited above.

In particular, the invention seeks to provide a threaded element thatcan be made up or broken out 10 times with a threaded element of themating type without causing galling under severe hydrocarbon wellexploitation conditions with Hertz pressures that can be employed thatmay be more than 300 MPa between the sliding contact surfaces, withsliding velocities of 0.1 μm/s and with slide lengths of up to onemeter.

The invention also seeks to avoid catastrophic galling leading suddenlyto an unacceptable degradation in the contact surfaces and necessitatingdiscarding or re-machining the threaded elements.

Still further, the invention seeks to provide a threaded element thatdoes not liberate any substances that are dangerous to the environmentsuch as lead or heavy metals for example.

Yet still further, the invention seeks to provide a threaded elementthat can be used with the same success both in arctic regions and intropical or equatorial regions and after periods at the bottom of wells,where the temperatures can reach or even exceed 160° C.

Still further, the invention seeks to provide a threaded element thatcan normally be used on the drill site or production site withoutapplying lubricant at that time, the necessary lubricant having alreadybeen applied at the factory producing the threaded element.

Yet still further, the invention seeks to ensure that the portions ofthe threaded element intended to come into sliding contact during makeupand coated with lubricant at the factory cannot be corroded duringtransport and storage.

Yet still further, the invention seeks to ensure that the lubricantdeposit produced at the factory can if necessary be repaired on site.

Of course, the invention seeks to ensure that the properties areobtained at a relatively low cost.

Further, the invention seeks to ensure that the threaded element can beused with success both with a mating threaded element in accordance withthe invention and with a compatible commercially available matingthreaded element.

Still further, the invention seeks to ensure that the same anti-gallingproperties is obtained with threaded elements comprising one or more“metal-metal” sealing surfaces and/or at least one makeup abutment inaddition to a threading.

Yet still further, the invention seeks to ensure that the sameanti-galling properties can be obtained with threaded elements forintegral threaded tubular connections or for threaded and coupledconnections, comprising all types of threadings (tapered, straight,single stage or with a plurality of stages, etc) with all types ofthread shapes (triangular, trapezoidal, etc.) with a constant or varyingthread width (wedge threads).

The invention provides a male or female threaded element comprising amale or female threading respectively, a lubricating substance beingdeposited in a thin layer at least on the surface of the threads of thethreading, this surface being treated to adsorb or absorb saidlubricating substance.

The term “thin layer of lubricating substance” means a layer with athickness of less than 0.10 mm.

The lubricating substance used is a homogeneous mixture of:

-   -   a) a thickening agent;    -   b) at least one extreme pressure (EP) additive including at        least one extreme pressure additive with a chemical action,        termed a chemical EP additive; and    -   c) an oil.

The term “homogeneous mixture” means, as is known, an intimate andstable dispersion of the constituents, such that the lubricatingsubstance has identical properties at all points.

The proportions of the three components of the lubricating substance areselected so that said lubricating substance has a consistency able toensure a self-fed lubrication regime and a film-forming nature.

The notion of a “self-fed lubrication regime” is known per se tocharacterize the fact that, in lubricating substances of the oil typeand of certain greases, the layer of lubricating substance is neverirreversibly destroyed but “self-heals” or “self-joins” as it is shearedoff during makeup.

Such a characteristic can be achieved with a range of consistency forthe lubricating substance at ambient temperature that is relativelywide, ranging from a semi-solid consistency similar to that of a highlyviscous varnish prior to drying to a pasty consistency that does notflow and resembles a wax.

It is necessary to combine the three components of the lubricatingsubstance, thickening agent, EP additive and oil, to solve the presentproblem. However, the lubricating substance can also comprise othersubstances, which are inert as regards the galling resistance, but areadded for other reasons (to color the layer, for example).

The thickening agent, as its name implies, makes the lubricatingsubstance thick, viscous, consistent, pasty but fluid to provide theself-fed lubricating regime and the film-forming properties. It can alsoact as a binder for the other constituents of the lubricating substance.

Two chemical families of thickening agent, organic and mineral, can bedistinguished:

-   -   a) organic thickening agents: non limiting examples of organic        thickening agents that can be cited are animal or vegetable        petroleum waxes, petrolatum waxes, oxidized petrolatum waxes,        sulphonated waxes, synthetic waxes and mixtures of these waxes,        tackifying petroleum resins, bitumens, polymers that are soluble        or dispersible in oil, liposoluble soaps, etc. In addition to        the properties cited above, this type of thickening agent can        advantageously have a protective function as regards corrosion        because of its chemical and physical characteristics.    -   b) mineral thickening agents: the mineral thickening agent can        be hydrophobic calcined silica, hydrophobic grafted bentonites        or titanium dioxide.

Extreme pressure (EP) additives are substances that are well known inthe lubricant field. Their performances can be measured by EP teststandards (4 ball test, Falex test, etc.).

By definition, chemical EP additives react with metallic parts incontact from a certain temperature generated by friction, creating achemical lubricating film. Among chemical EP additives the followingones are known:

-   -   chemical EP additives based on sulfur or containing sulfur, such        as for example hydrocarbons or sulfur-containing esters sold as        a “sulfur-containing product”, metallic dithiocarbamates,        neutral or overbased metallic sulphonates;    -   chemical EP additives based on phosphorus, such as phosphoric        acids or esters;    -   chemical EP additives based on sulfur and phosphorus, such as        metallic dithiophosphates, in particular of zinc;    -   chemical EP additives based on chlorine, in particular        chlorinated paraffins;    -   modified or non-modified fatty acids or esters, complex esters,        etc.

These chemical EP additives are generally produced and sold diluted in amineral oil, but the term “chemical EP additives” as used in theremainder of the present document will refer to the undiluted activeingredient.

The chemical EP additive or additives used are selected from knownadditives to allow operation without galling at a Hertz pressure of 1000MPa or more.

They are also selected so as to be physically and chemically compatiblewith the selected thickening agent: they must, therefore, be perfectlymiscible with the thickening agent but must not react with it as theirextreme pressure properties would be severely diminished.

These chemical EP additives can be used alone or as a mixture to benefitfrom maximum synergy in performance.

The term “oil” as used in the lubricating substance means both an oilthat is specifically added and an oil in which the thickening agentsand/or EP additives, in particular chemical EP additives, are dilutedwhen supplied.

The oil used can be a cut from distilling petroleum products known as“inorganic base”, but it can also be a synthetic base obtained bychemical reaction such as polyalphaolefins, polyisobutenes, esters, etc.it can also be a vegetable based oil (rapeseed oil, sunflower oil, etc.)or an animal oil. It can also be a mixture of such bases.

Preferably, the chemical EP additive or additives and thickening agentare soluble in the oil, which enables to disperse the chemical EPadditive or additives with the thickening agent and obtain a perfectlyhomogeneous lubricating substance.

Preferably, the thickening agent has chemical molecules with a markedpolar nature. Such a feature can in particular make the lubricant adhereto a substrate.

Preferably, the thickening agent is chemically stable up to atemperature of 120° C. or more, preferably 160° C. or more.

Optionally, the EP additive or additives also comprise at least one EPadditive with a physical action, preferably in the form of solidsubmicronic particles to produce the lubricating substance in the formof a homogeneous mixture.

EP additives with a physical action, known as physical EP additives,intercalate themselves between the contact surfaces in the form of afilm that can shear along the characteristic cleavage planes of theircrystalline structure and parallel to the plane of movement, or simplyin readily deformable planes. The first category (cleavage) includesgraphite, molybdenum, tungsten or tin disulfides, boron nitride, etc.,and the second category includes PTFE, polyamide, polyurea typepolymers, etc.

Preferably, at least one of the components from the assembly of EPadditives has anticorrosion properties.

The total content of EP additives is preferably in the range 5% to 75%%, depending on the type of EP additive used.

In a first preferred implementation, the total content of EP additivesis in the range 5% to 50% and highly preferably in the range 15% to 32%by weight.

Advantageously in this first implementation, the lubricating substancecomprises a plurality of chemical EP additives, preferably nonchlorinated additives.

In a first variation of the first implementation, the content ofthickening agent in the lubricating substance is in the range 5% to 60%by weight and preferably in the range 8% to 40% by weight; this resultsin an oil content in the lubricating substance which is in the range 30%to 75% and preferably in the range 40% to 60% by weight.

In a second variation of the first implementation, enabling to have amore solid deposit consistency, the content of thickening agent in thelubricating substance is in the range 60% to 80% by weight; this resultsin an oil content in the lubricating substance in the range 5% to 20% byweight.

In a second preferred implementation in which the chemical EP additiveor additives comprise a chlorinated paraffin, the content of thickeningagent in the lubricating substance is in the range 25% to 60% by weight,and the total EP additive content in the lubricating substance is in therange 40% to 75%; this results in an oil content in the lubricatingsubstance in the range 0.5% to 15% by weight.

The contents of thickening agent and EP additives given for thedifferent compositions of the present document correspond to thecontents of active substances of the indicated constituents.

Preferably, the weight of the layer of lubricating substance on thethreaded element is in the range 0.1 g/m² to 40 g/m².

In a variation, the surface of the threads, treated to adsorb or absorbthe lubricating substance, is the surface of a layer selected from thegroup formed by phosphatation layers, oxalation layers and metal layers.

In a variation, the surface of the threads is treated to endow it with acontrolled roughness so as to adsorb or absorb the lubricatingsubstance. Such a treatment can, for example, be sanding, shot blasting,etching or the like.

Preferably, the surface of the threading threads is treated to adsorb orabsorb the lubricating substance over a depth in the range 0.003 mm to0.080 mm.

Advantageously, the lubricating substance is also deposited on eachsealing surface when the threaded element under consideration comprisessuch sealing surfaces.

Advantageously again, the lubricating substance is also deposited oneach abutment surface when the threaded element under considerationcomprises such abutments.

Advantageously again, all the surfaces on which the lubricatingsubstance is intentionally deposited as a thin layer are surfaces thatare treated to adsorb or absorb the lubricating substance.

The present invention also aims to protect a galling-resistant threadedtubular connection that comprises a male threaded element and a femalethreaded element, each provided with a corresponding threading, thethreadings being made up one into the other during connection, in whichat least one of the two threaded elements is a threaded element of theinvention as described above.

In a variation of this threaded connection, only one of the two threadedelements is a threaded element of the invention as described above, theother threaded element comprising a thin layer of the lubricatingsubstance defined above deposited directly on at least the surface ofthe threads.

The lubricating substance is a homogeneous mixture of:

-   -   a) a thickening agent;    -   b) at least one extreme pressure additive, the extreme pressure        additive or additives being physically and chemically compatible        with the thickening agent and comprising at least one extreme        pressure additive with a chemical action, termed a chemical EP        additive, that can be used at Hertz pressures of 1000 MPa or        more; and    -   c) an oil.

The term “directly deposited thin layer of lubricating substance” meansthat the surface of the threads under consideration has not been treatedto adsorb or absorb the lubricating substance.

The present invention also aims to protect a method for producing a thinlayer of a lubricating substance on a male or female threaded elementfor a galling-resistant threaded tubular connection as described above,the threaded element comprising a male or female threading respectively.

The method of the invention comprises the following steps:

-   -   a) preparing a homogeneous liquid mixture comprising:        -   a volatile solvent;        -   a thickening agent;        -   at least one extreme pressure additive, the extreme pressure            additive or additives being physically or chemically            compatible with the thickening agent and comprising at least            one extreme pressure additive with a chemical action that            can be used at Hertz pressures of 1000 MPa or more; and        -   an oil;    -   b) applying a thin layer of substantially uniform thickness of        said liquid mixture at least to the surface of the threads of        the threaded element; and    -   c) evaporating off the solvent naturally or forcedly.

The term “volatile solvent” means any petroleum cut with distillationtemperatures in the range 40° C. to 250° C. These volatile solventsinclude special gasolines, white spirits, burning oils, aromaticproducts such as benzene, toluene, xylene, etc.

Optionally, at least the surface of the threads of the threaded elementis treated to adsorb or absorb the lubricating substance to be applied.

Preferably, the viscosity of the liquid mixture, measured by FORD n°4cup, corresponds to a duration in the range 10 s to 30 s, preferably inthe range 15 s to 25 s.

Preferably again, the layer of liquid mixture is applied by spraying.

As an alternative, it can be applied by any other means: immersion,painting, sprinkling.

The solvent can be evaporated off naturally or in a forced manner, inparticular by moderate heating of the threaded element or by hot airconvection.

The following figures provide non-limiting illustrations of a number ofimplementations of the invention.

FIG. 1 shows a type of threaded and coupled connection comprising 4threaded tubular elements that may be used by the invention.

FIG. 2 shows a further type of threaded and coupled connectioncomprising 4 threaded tubular elements that may be used by theinvention.

FIG. 3 shows an integral type threaded type connection comprising 2threaded tubular connections that may be used by the invention.

FIG. 4 shows a few male threads of a male threaded tubular element ofthe commerce shown in FIG. 1.

FIG. 5 shows a few female threads of a female threaded tubular elementof the invention of the type shown in FIG. 1.

FIG. 6 shows a detail of FIG. 5.

FIG. 7 shows the stabbing phase at the beginning of make up of the maleand female threads of FIGS. 4 and 5.

FIG. 8 shows the same male and female elements of FIGS. 4 and 5 oncemake up is completed.

FIG. 9 shows a few male threads of a male threaded tubular element for athreaded tubular connection of the invention of the type shown in FIG.2.

FIG. 10 shows a few female threads of a female threaded tubularconnection of the type shown in FIG. 2.

FIG. 11 shows the stabbing phase at the beginning of make up of the maleand female threads of FIGS. 9 and 10.

FIG. 12 shows a detail of FIG. 11.

FIG. 13 shows the same male and female elements of FIGS. 9 and 10 oncemake up is completed.

FIG. 14 shows a variation of FIG. 9.

FIG. 15 shows the male and female threads of FIGS. 14 and 10 once makeup is completed.

FIG. 16 shows the free end zone of the male element shown in FIG. 2.

FIG. 17 shows a housing zone inside a female threaded tubular element ofthe invention shown in FIG. 2.

FIG. 18 shows the free end zone of FIG. 16 and the housing zone of FIG.17 after make up of the threaded elements.

FIG. 19 is a graph representing the makeup curve for a threadedconnection of FIGS. 9 to 13 and 16 to 18.

FIG. 20 is a graph representing, for a threaded connection of FIGS. 9 to13 and 16 to 18, the relative evolution of the shouldering torque duringmake up and that of the initial breakout torque as a function of thenumber of makeup-breakout cycles.

FIG. 1 shows a threaded connection 100 in accordance with APIspecification 5CT between two metal pipes 101 and 101′ using a coupling102 and comprising 2 threaded connections.

Each end of pipe 101, 101′ comprises a male element 1,1′ comprising amale tapered threading 103, 103′ with “round” threads and terminates ina male end surface 109, 109′.

Coupling 102 comprises 2 female elements 2, 2′ symmetrically disposedwith respect to the median plane of the coupling, each female elementcomprising a female tapered threading 104, 104′ with threads that matewith the male threads.

Male threadings 103, 103′ are made up into mating female threadings 104,104′.

API specification 5B defines the thread shape, dimension, threadingtaper, pitch, etc for this type of connection.

Although not shown, a connection with “buttress” type threadings canalso be used under API specification 5CT and 5B disposed in the same wayas that of FIG. 1, but with trapezoidal threads.

FIG. 2 shows a threaded and coupled connection 200 with two maleelements 1,1′ and two female elements 2,2′ with tapered threadings 203,204 and with trapezoidal threads, coupling 202 having a lug 206 in itscentral portion between the female elements, the lug enabling to makethe fluid flow in a non turbulent way in pipes 201, 201′, and to providefemale abutments 210 which bear against the male abutments 209constituted by the annular end surfaces of the pipes.

Tapered male and female sealing surfaces 207 and 208, disposed on thenon threaded portions and radially interfering so as to produce anelastic contact pressure between them enable to provide a seal for theconnection of FIG. 2 in known manner.

FIG. 3 shows an integral threaded connection 300 between two pipes 301and 302 comprising two-stage straight threadings.

The end of pipe 301 comprises a male element 1 comprising a straighttwo-stage male threading 303, 303′, a tapered male shoulder surface 307in a half dovetail between the two male thread stages and abutments 309,309′ at each end of the male element.

The end of pipe 302 comprises a female element 2 that mates with themale element 1 and comprises a straight two-stage female threading 304,304′, a tapered female shoulder surface 308 in a half dovetail betweenthe two female thread stages, and abutments 310, 310′ at each end of thefemale element.

The male and female threadings of coupling 300 have trapezoidal threadsand normally have no radial interference after makeup.

In the connected state, shoulders 307, 308 form the principal abutment,abutments 309, 309′, 310, 310′ only acting as a backup abutment in caseof sinking of the principal abutment.

Tapered surfaces 311′, 312′ on the male and female elements respectivelyform an internal pair of metal-metal sealing surfaces, in the vicinityof the end of the male element. In the vicinity of the end of the femaleelement, the tapered surfaces 311, 312 form, an external pair ofmetal-metal sealing surfaces. The external pair of sealing surfaces 311,312 could also be placed between shoulders 307, 308 and the largediameter threading stage 303, 304.

FIG. 4 shows a longitudinal section of a few triangular threads 11 ofthe male tapered threading 103 of FIG. 1.

Male threads 11 comprise two rectilinear flanks 13, 15 each making anangle of 30° with respect to the normal YY to axis XX of the threadedelement and either side of that normal, a male rounded thread crest 17and a male thread root 19, also rounded.

Flank 15, the normal to the surface of which is directed towards thefree male end 109, is the flank known as the stabbing flank because themale stabbing flank rests on the female stabbing flank during engagementof the male and female threads for connection by makeup.

Flank 13, the normal to the surface of which is directed towards theside opposite the male free end 109, is the load flank. The load flankssupport the axial tensile load on the threaded connections. Surfaces 13,15 and zones 17, 19 of the male threads are as machined.

FIG. 5 shows a longitudinal section through a few triangular threads 12of the female tapered threading 104 of FIG. 1.

The form of female threads 12 corresponds to the form of male threads11, each with a stabbing flank 16 and a load flank 14, placed at 30°either side of the normal YY to the axis of the threaded element, afemale thread crest 20 and a female thread root 18.

Surfaces 14, 16 and zones 18, 20 of the female threads are treated toabsorb or adsorb a lubricating substance and to this end, comprise alayer 32 for conversion by manganese phosphatation with a thickness of0.006 mm produced on the surfaces of the as machined thread. Themanganese phosphatation layer is well suited to treating unalloyed orlight alloy steel threaded elements.

Other phosphatation layers are also possible, such as a zincphosphatation layer, for example.

In the case of steel threaded elements with a high chromium content or anickel based alloy, it may be advisable to produce the layer byoxalation or by means of a deposit of copper metal.

The thickness desired for the different layers is of the same order ofmagnitude as that for the manganese phosphatation.

The treated surface of the female threads 12 is coated with a thin layer22 of a lubricating substance that is partially adsorbed or absorbedinto the phosphatation layer and which covers the latter by a thicknessof a few microns in a substantially uniform manner over the treatedsurface of threads 12. The ratio between the weight of the adsorbed orabsorbed layer in the phosphatation layer and the weight of the layerover the phosphatation layer is about 1/1.

The following compositions are examples of compositions (weight %) andof weight of layer (g/m²) of suitable lubricating substance.

EXAMPLE 1

petroleum paraffin wax: 19% sulfur-containing product:  6% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 59% Weightof deposit: 20 g/m²The lubricating substance comprises three chemical EP additives, namelythe sulphur-containing product, the overbased sulphonates and themetallic dithiophosphate, which are oil-soluble constituents. The wax isalso soluble in the oil.

EXAMPLE 2

oxidized petrolatum wax:  29% sulfur-containing product:  6% overbasedcalcium sulphonates:  13% metallic dithiophosphate (Zn):  3% mineraloil:  49% Weight of deposit:  20 g/m² Kinematic viscosity of deposit at±100° C. 260 cSt

It should be noted that oxidized petrolatum waxes are verytemperature-stable compounds that are not deteriorated chemically whenthe temperature is maintained at 160° C. Such a chemical stabilityenables the threaded connections to be lowered to the bottom of wellswhere the temperature can reach 160° C. without irreversible changes inthe characteristics of the wax; the threaded connections can then beraised from the well for breakout before being made up again and droppedagain into the same well or into another well.

EXAMPLE 3

petrolatum wax: 31% sulfur-containing product:  6% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 47% Weightof deposit: 24 g/m²

EXAMPLE 4

tackifying petroleum resin: 30% sulfur-containing product:  6% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 48% Weightof deposit: 21 g/m²

EXAMPLE 5

sulphonated wax: 30% sulfur-containing product:  6% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 48% Weightof deposit: 21 g/m²

EXAMPLE 6

bitumen: 30% sulfur-containing product:  6% overbased sulphonates: 13%metallic dithiophosphate:  3% mineral oil: 48% Weight of deposit: 22g/m²

EXAMPLE 7

aluminium stearate: 30% sulfur-containing product:  6% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 48% Weightof deposit: 23 g/m²

EXAMPLE 8

lipophilic bentonite:  9% sulfur-containing product:  7% overbasedsulphonates: 13% metallic dithiophosphate:  3% mineral oil: 68% Weightof deposit: 14 g/m²

EXAMPLE 9

polyalkylmethacrylate (organic thickening agent): 12% sulfur-containingproduct:  6% overbased sulphonates: 12% metallic dithiophosphate:  4%mineral oil: 66% Weight of deposit: 23 g/m²

EXAMPLE 10

oxidized petrolatum wax: 39% polyisobutene  2% chlorinated paraffin: 59%Weight of deposit: 21 g/m²

In this Example 10, the chlorinated paraffin has an oily consistency; asmall proportion of oil is added in the form of polyisobutene (syntheticbase).

The use of chlorinated paraffin as a chemical EP additive renders thiscomposition more particularly suitable for use with certain stainlesssteel threaded elements (not susceptible to corrosion by chlorine orchlorides) or nickel alloy threaded elements.

EXAMPLE 11

oxidized petrolatum wax:  67% sulfur-containing product:  5% overbasedcalcium sulphonates:  12% metallic dithiophosphate (Zn):  5% mineraloil:  11% Weight of deposit:  23 g/m² Kinematic viscosity of deposit at+100° C.: 560 cSt

In all of the above examples, the deposits of lubricating substancesobtained are smooth because of the film-forming nature of thelubricating substance and the liquid mixture from which it originates.

In all of the above examples except for Examples 5 and 9, the depositsof the lubricating substance obtained have a waxy, adhesive appearance,do not flow and thus have a pasty consistency at ambient temperature; byway of indication, the viscosity of such deposits is in the range 100cSt to 1000 cSt at +100° C., the temperature that can be obtained whenmaking up the threaded elements.

In the case of Examples 5 and 9, the appearance of the deposit is morethat of a very viscous varnish and its consistency is semi-solid.

In all of the examples apart from Example 10, the lubricating substancecomprises three chemical EP additives as the EP additive, the totalcontent of EP additive being around 20-25%.

In Examples 1 to 9, the ratio between the sulfur-containing product,overbased sulphonates and metallic dithiophosphate is substantially2:4:1. In Example 11, it is substantially 1:2:1.

The content of oil in the lubricating substance varies widely dependingon the nature of the thickening agent and/or EP additives and thedesired consistency:

-   -   about 50% for Examples 1 to 7;    -   about 65-70% for Examples 8 (thickening agent=lipophilic        bentonite) and 9 (more flowing consistency);    -   about 10% for Example 11 (relatively solid waxy consistency);    -   only about 2% for Example 10 because of the oily consistency of        the proportion of paraffin selected.

In all of the examples comprising an organic thickening agent, i.e., inall of the examples except for Example 8, the thickening agent containschemical molecules with a marked polar nature, which allow it to adhereto the treated metallic surface of the threads and give it a hydrophobicnature. Such an adhesive hydrophobic nature allows the thin layer 22 oflubricating substance to perfectly cover the treated surface of thethreads and to protect this surface against corrosion, in particularwhen the pipes are stored with their threaded elements prior to use.

All the compositions of these 11 examples produce a welding load in theASTM D2596 “4 ball” test (EP test) of more than 800 kg and a wear markdiameter of 0.35 to 0.37 mm after 1 hour at 392 N (40 kgf) of loadduring ASTM D2266 wear tests.

All of the chemical EP additives of the 11 examples are physically andchemically compatible with the corresponding thickening agents. Thechemical EP additives must remain stable until they are subjected totemperatures resulting from local rupture of the lubricating film andenabling those additives to then react chemically with the metallicsurfaces in contact to form constituents preventing or delaying gallingeven when the contact pressure exceeds 1000 MPa.

In addition to a thickening agent, EP additives and an oil, thelubricating substance can optionally comprise less than 5% of a coloranthaving no action as regards the anti-galling properties but intended toindicate the presence of a thin layer of the lubricating substance ofthe invention (traceability and differentiation over standard APIgreases).

Thus the lubricating substance can comprise 2.5% of powdered carbonblack to endow the lubricating substance with a highly homogeneous blackcolor, or 0.12% of fluorescein (Fluorescent Green Light) to endow thelubricating substance with a dark green color.

FIG. 7 shows female threads 12 during the stabbing phase during theirconnection to male threads 11 by makeup.

The layer of lubricating substance 22 prevents direct contact of the asmachined male stabbing flanks 15 and female stabbing flanks 16 treatedby phosphatation.

Because makeup has only just started and because of the tapereddisposition of the threadings, there remains a free space between thelayer 22 and the surface of the male thread at the load flanks 13, 14and the thread crests and roots.

Layer 22 supports the weight of pipe 101 at the stabbing flanks, pipe101 being made up in the vertical position above coupling 102 alreadyconnected to pipe 101′ and the high torque provided by the makeup tongs.

Even a slight misalignment of the axes of the male and female threadedelements 1,2 during engagement would, in the absence of any lubricatinglayer, result in ploughing of the stabbing flank surfaces and very rapidgalling of the contacting flanks: it then would be impossible to breakout the galled threaded connections and in any event, the deterioratedsurfaces of the thread would have to be reconditioned.

The presence of a thickening agent and of oil in the lubricatingsubstance of layer 22 and the viscosity of the lubricating substanceensure that in the presence of shear stresses, there is a self-fedlubrication regime that is typical of an oil or grease. This results inthe absence of cracking of the lubricating substance on shear forexternal operating temperatures in the range −50° C. to +50° C.; it canalso be said that the lubricating substance self-heals or self-joins asit is being sheared.

The phosphatation layer 32 on the surface of the female threads 12 canefficiently retain the lubricating substance on the surface of thesethreads.

Under extreme pressure conditions when self-feeding of the lubricatingsubstance is interrupted locally, the chemical extreme pressure additivetakes up the baton for preventing galling.

FIG. 8 shows the male and female threads 11, 12 in the final made upposition.

The lubricating substance of the thin layer 22 is distributed in theclearances between the helical surfaces of the threads during makeup. Itcomes between load flanks 13, 14 and between stabbing flanks 15, 16 andit more or less fills the clearances between thread crests and roots 17,18, 19, 20 following the pairing due to dimensional tolerances.

For this reason, excess lubricating substance is not ejected into thewell and the threaded elements cannot be deformed by the pressuresexerted by a great excess of lubricating substance.

Breakout of the connected threads leads to separation of layer 22 into 2parts, which separation is random in nature within that layer.

Nevertheless the remainders of the layers on the male and female threadscan allow at least 10 makeup-breakout cycles to be carried out withoutthe onset of galling.

On the other hand the inventors have noted that simply adding aconventional API 5A2 type grease reduced with respect to the standardquantities required in a manner to simply fill the clearances betweenthe threads rapidly leads to galling after a few makeup/breakout cyclesif addition is not renewed between cycles.

FIG. 9 shows a longitudinal section of a few male trapezoidal threads 51of the male tapered threading 203 of FIG. 2.

Male threads 51 comprise four rectilinear faces, namely:

-   -   a load flank 53;    -   a stabbing flank 55;    -   a thread crest 57;    -   a thread root 59.

The thread crests and roots are parallel to the pitch taper of threading103.

In a variation, not shown, they could be parallel to the axis of theconnection, the radial height of the stabbing flank then being greaterthan that of the load flank.

Load flank 53 makes a slightly negative angle A with the normal to theaxis of the threaded element, for example −3°, such that there is aslight overhang.

Stabbing flank 55 makes a positive angle B with the normal to theconnection axis such that threads 51 are narrower at their base than atthe crest 57, which facilitates machining.

The 4 faces 53, 55, 57, 59 of threads 51 are coated in the as machinedstate with a deposit 21 that is a few micrometers thick of the samelubricating substance as that formed by deposit 22 in FIG. 5. The samecompositions and the same weights of layer can be applied as thosedescribed for FIG. 5.

FIG. 10 shows a longitudinal cross section of a few female trapezoidalthreads 52 of the female tapered threading 204 of FIG. 2.

Female threads 52 comprise four rectilinear faces with a shape anddisposition that correspond to those of the male threads 51, namely:

-   -   a load flank 54 with a slightly negative angle A;    -   a stabbing flank 56 with a positive angle B;    -   a thread crest 60;    -   a thread root 58.

Faces 54, 56, 58, 60 are treated by manganese phosphatation in order toproduce a 0.006 mm thick phosphatation layer 32, as is the case withFIG. 5.

The thus treated surface of the female threads 52 is coated with a thinlayer 22 of the same lubricating substance as that described for FIG. 5.

This lubricating substance is absorbed or adsorbed on the treatedsurface of threads 52 and covers this surface to a thickness of a fewmicrometers in a uniform manner. The same compositions and the sameweights of layers can be applied as those described in respect of FIG.5.

As for FIG. 5, manganese phosphatation can be replaced by anothersurface treatment that is more suitable to the metal of the threadedelement in order to produce surfaces that are suitable for adsorbing orabsorbing the lubricating substance.

FIG. 11 shows female threads 52 during the stabbing phase when beingconnected to male threads 51 by makeup.

At the stabbing flanks 55, 56 (see FIG. 12), layers 21, 22 form just onelayer 23 whereas they are distinct between the other faces that are notin contact during the stabbing phase.

Layer 23 supports the weight of pipe 201 to be connected, the makeuptorque and possibly any side forces if the axis of the male elementmakes an angle with the axis of the female element.

When makeup is complete (FIG. 13), the lubricating substancesubstantially fills all the clearances between threads 51, 52 andprevents direct contact between the load flanks 53, 54 under tension andbetween the female thread crest 60 and the male thread root 59 whichradially interfere.

FIG. 14 shows a variation of FIG. 9 in which layer 21 of lubricatingsubstance is not directly produced on the as machined surface of themale threads but on an initially deposited phosphatation layer 31similar in nature and thickness to that 32 on the surface of the femalethreads 52 of FIG. 10.

Such a configuration enables to better hold back the lubricatingsubstance on the surface of the male threads and to obtain a connectionshown in FIG. 14 with the corresponding female threads of FIG. 10, whichconnection is particularly suitable for undergoing many makeup-breakoutcycles without the risk of galling.

Such a threaded connection of FIG. 15, on the other hand, requiresphosphatation both on the coupling 202 and on pipes 101, 101′ and thusis more expensive than the connection of FIG. 13.

FIG. 16 shows the free end zone of pipe 201 and thus of the malethreaded element of FIG. 2.

In FIG. 16, layer 21 of the lubricating substance covers not only thesurface of male threads 51 of FIG. 9 but also the whole of the externalperipheral surface of the male element beyond the threading, and moreparticularly at 27 the male sealing surface 207 and at 29 the maleabutment surface 209 at the end of the pipe. The weight of the layerdeposited on surfaces 207, 209 is substantially similar as thatdeposited on the surface of the male threads.

FIG. 17 shows the female housing zone for the male end of coupling 202of FIG. 2.

In FIG. 17, the internal surface of the female element between threading204 and lug 206 is treated in the same manner as the surface of femalethreads 52 of FIG. 10 by manganese phosphatation (layer 32) and iscoated with a layer 22 of lubricating substance, like the surface ofthose threads 52.

More particularly, layers 32 and 22 coat the female bearing surface 208at 38 and 28 and the female abutment 210 at 40 and 30.

These layers can readily extend over the internal peripheral surface ofthe lug 206 and over the external peripheral surface of the coupling202.

The thickness of the phosphatation layer is substantially identical forthe sealing surface 208, the female abutment 210 and the female threads52.

Similarly, the weight of the layer of lubricating substance issubstantially identical for the sealing surface 208, the female abutment210 and the female threads 52.

FIG. 18 shows the connection in the made up position of the male freeend of FIG. 16 with the corresponding female zone of FIG. 17.

During makeup, the layers of lubricating substances 27, 28 come intocontact with each other.

As make up continues, these layers held back by the phosphatation layer38 prevent direct contact of the metal surfaces of the sealing surfacesand prevent them from galling in particular when surfaces 207, 208 areonly slightly inclined and when contact of these surfaces up to thefinal made up position is produced over a considerable length.

The mechanism for the action of the lubricating substance is the same asthat at the thread surfaces.

At the very end of makeup, layers 29, 30 at the level of the abutmentsurfaces 209, 210 come into contact and prevent these surfaces fromgalling by the same mechanism.

The phosphatation layer 40 also acts to hold back as much of the film oflubricating substance as possible. Although not shown, one could alsothink of depositing the lubricating layer at 27 and 29 (male sealingsurface and abutment) not directly on the as machined metal surface buton surfaces treated by phosphatation, as is the case in FIG. 17.

It is also easy to apply the teaching of FIGS. 4 to 18 to straightthreadings with one or more stages such as those at 303, 303′, 304, 304′of the integral threaded connection of FIG. 3 as well as to the abutmentand sealing surfaces existing on said connection.

Other implementations that have not been described are also encompassedby the present invention, in particular when the phosphatation layer isproduced at the surface of the thread of the male threaded element andnot the female threaded element (opposite configuration to that shownfor FIGS. 1-18).

The invention is applicable to any male or female threaded elementregardless of the disposition of the threading or the threaded portions,to any thread form, to any thread width, which may be constant or mayvary along the threading, to interfering or non-interfering threads,with or without contact or interference over the two flanks of the samethread, whether the threaded connection obtained is of a threaded andcoupled type or integral type. It is also applicable regardless of thenumber, form and disposition of the bearing surface and abutment.

We shall now describe non-limiting examples of a method for depositingthe lubricating substance in a thin layer on the surface of threads,sealing surfaces and/or abutments to obtain the galling-resistantconnections described above.

A liquid mixture is prepared with a viscosity that is measured using aFORD n° 4 cup at 25° C.; some non-limiting examples of the formulationare given below. The numbers for these examples of the liquid mixtureformulation respectively correspond to those used in the above examplesof the composition of the lubricating substance, the “dry extract” ofthe lubricating substance corresponding to the liquid mixture of thesame example.

EXAMPLE 1

special hydrocarbon solvent: 20% mineral oil: 47% petroleum paraffinwax: 15% sulfur-containing product:  5% overbased sulphonates: 10%metallic dithiophosphate:  3% FORD n ° 4 cup viscosity: 20 s

EXAMPLE 2

special hydrocarbon solvent (white spirit): 23% mineral oil: 37%oxidized petrolatum wax: 22% sulfur-containing product:  5% overbasedsulphonates: 10% metallic dithiophosphate:  3% FORD n ° 4 cup viscosity:20 s

EXAMPLE 3

special hydrocarbon solvent: 20% mineral oil: 37% petrolatum wax: 25%sulfur-containing product:  5% overbased sulphonates: 10% metallicdithiophosphate:  3% FORD n ° 4 cup viscosity: 21 s

EXAMPLE 4

special hydrocarbon solvent: 22% mineral oil: 37% tackifying petroleumresin: 23% sulfur-containing product:  5% overbased sulphonates: 10%metallic dithiophosphate:  3% FORD n ° 4 cup viscosity: 18 s

EXAMPLE 5

special hydrocarbon solvent: 22% mineral oil: 37% sulphonated wax: 23%sulfur-containing product:  5% overbased sulphonates: 10% metallicdithiophosphate:  3% FORD n ° 4 cup viscosity: 16 s

EXAMPLE 6

special hydrocarbon solvent: 22% mineral oil: 37% bitumen: 23%sulfur-containing product:  5% overbased sulphonates: 10% metallicdithiophosphate:  3% FORD n ° 4 cup viscosity: 17 s

EXAMPLE 7

special hydrocarbon solvent: 20% mineral oil: 39% aluminium stearate:23% sulfur-containing product:  5% overbased sulphonates: 10% metallicdithiophosphate:  3% FORD n ° 4 cup viscosity: 18 s

EXAMPLE 8

special hydrocarbon solvent: 20% mineral oil: 54% lipophilic bentonite: 8% sulfur-containing product:  5% overbased sulphonates: 10% metallicdithiophosphate:  3% FORD n ° 4 cup viscosity: 17 s

EXAMPLE 9

special hydrocarbon solvent: 20% mineral oil: 52% 50%polyalkylmethacrylate: 10% sulfur-containing product:  5% overbasedsulphonates: 10% metallic dithiophosphate:  3% FORD n ° 4 cup viscosity:22 s

EXAMPLE 10

special hydrocarbon solvent: 42% oxidized petrolatum wax: 23%polyisobutene:  1% chlorinated paraffin: 34% FORD n ° 4 cup viscosity:20 s

EXAMPLE 11

special hydrocarbon solvent (heptane): 40% mineral oil:  7% oxidisedpetrolatum wax: 40% sulfur-containing product:  3% overbasedsulphonates:  7% metallic dithiophosphate:  3% FORD n ° 4 cup viscosity:20 s

All these liquid mixtures are intimate and stable; thus, they arehomogeneous and after eliminating the solvent, produce a homogeneouslubricating substance as defined above.

These liquid mixtures can readily be prepared in advance and stored inclosed vessels prior to use. If necessary, the mixture can simply behomogenized prior to use.

The mixture has to be applied in a thin layer to the male and femalethreaded elements of FIG. 2 with a substantially uniform thickness andmore particularly for each of the threaded elements on their threading203, 204, on the sealing surface 207, 208 and on the abutment 209, 210.

The fact that the organic thickening agents used for the mixtures ofExamples 1 to 7 and 9 to 11 contain chemical molecules with a markedpolar nature allows the liquid mixture to adhere better to the substrateto be coated.

The content of solvent in the liquid mixtures is of the order of 20% forExamples 1 to 9 and of the order of 40% for Examples 10 and 11. Itvaries as a function of the consistency of the dry extract obtainedafter evaporation of the solvent and the nature of the solvent (whitespirit, heptane, etc.).

The male threaded elements 1 that are at the end of pipes 201 are placedin the as machined state under a spray head of the type used tophosphate the male threaded elements.

The spray head is supplied at low pressure (1 to 3 bars relative) withthe liquid mixture and sprays the liquid mixture over the externalsurface of the threaded elements.

Because of the low viscosity of the liquid mixture, it distributesitself in a film of uniform thickness over the entire periphery of thethreading 203, the sealing surface 207 and the abutment 209.

The thickness of the liquid mixture film is a function of the viscosityof the mixture which is itself a function of the content of oil andvolatile solvent: a large content of oil and volatile solvent reducesthe viscosity of the mixture and thus the thickness of the liquid film.

The solvent is then evaporated off completely to obtain a layer oflubricating substance with a substantially uniform thickness.

The drying time for the liquid mixture is linked to the evaporation timefor the solvent, which is a function of the nature of the solvent(shorter time for heptane than for white spirit, for example) and of thedrying temperature.

Female threaded elements 2 to be coated are located inside couplings202.

Couplings 202 have already undergone, in known manner, a manganesephosphatation treatment which has coated the threading 204, the sealingsurface 208 and the abutment 210 of each of the two female threadedelements with a fine phosphate conversion layer about 0.006 mm thick.

Couplings 202 are then individually placed in paint tanks, which containspray nozzles supplied with the liquid mixture and directed so as toproject fine droplets of liquid mixture onto the threading, the sealingsurface and the abutment of each female threaded element.

The thickness of the resulting film of liquid mixture is a function ofthe viscosity of the liquid mixture, the spray pressure, the spraynozzle diameter and the spray duration.

The couplings are then withdrawn from the paint tank and dried bycirculating hot air until the solvent has been completely evaporatedoff.

Each coupling 202 is then made up in the factory in a standard mannerusing one of its two female threaded elements onto a male threadedelement of one of the two ends of pipe 101.

In a known manner, the second female threaded element of the coupling202 that is not made up and the second male threaded element that is notmade up at the other end of pipe 201 are then protected by protectors inorder to prevent pollution of these threaded elements by abrasiveparticles during transport or storage, which can deteriorate the sealingperformance during use in a petroleum well.

The applied lubricating substance has hydrophobic and anti-corrosiveproperties that can protect the threaded elements from corrosion duringstorage and transport.

If, however, the lubricating substance became polluted, it could be easyto eliminate the layer as if it were a grease, by high water pressure orby petroleum solvent, to apply a new film of liquid mixture, for exampleusing a brush, and to evaporate off the solvent.

Adding colorant to the lubricating substance can facilitate checkingthese operations of eliminating the layer of polluted lubricatingsubstance and its reconstitution.

Alternatively, standard API type grease can be applied to the threadedelement, coated or uncoated or partially uncoated of lubricatingsubstance. The lubricating substance is completely compatible with APItype grease.

Such repair procedures are not possible with sliding varnishes.

We now show, in FIG. 19, two makeup curves obtained with VAM TOP®threaded connections from the VAM® catalogue, n° 940 edited by theApplicant, with dimensions of 5½″×17 lb/ft (external pipe diameter 139.7mm and pipe thickness 7.72 mm), of light alloy steel, heat treated,grade L80 (elastic limit of 551 MPa or more).

FIG. 19 shows the makeup torque T up the ordinate as a function of thenumber of turns N for two tests A and B, curves A and B having beenoffset along the X axis for easier reading.

Curve A relates to a connection of the invention: the male threadedelement is similar to that of FIG. 9 (as machined trapezoidal threadscoated with the lubricating substance with the composition of Example 2)and the female threaded element is similar to that of FIG. 10(trapezoidal threads phosphated with manganese and coated with the samelubricating substance with the composition of Example 2).

Curve B relates to a reference connection lubricated in a standardmanner with API 5A2 grease.

In curves A and B, once engagement has occurred between the male andfemale threaded element, the makeup torque rises steadily because ofsliding of the corresponding faces of the threads under contactpressure. The makeup torque increases significantly as the radialinterference between the male and female threads resulting from thedimensional characteristics of the threaded connections is high.

Note at a given time the increase in the slope of the makeup curve whichshows the appearance of radial interference between the sealing surfaces207-208. Curves A and B in FIG. 19 are characteristic of threadedconnections with high interference between the sealing surfaces.

From point S, the makeup torque increases almost vertically and showsthe coming into contact of abutments 209/210.

Point F indicates the final makeup torque, which is located between theminimum makeup torque (T_(min)) and the maximum makeup torque (T_(max))specified for this type of threaded connection.

Curve A obtained for a threaded connection of the invention is verysimilar to that of B obtained for a threaded connection lubricated by anAPI grease both from its appearance and from the shouldering torqueT_(S) and the final torque T_(F). This shows that the coefficient offriction of the lubricating substance of the present invention issimilar to that of the standard API grease.

For the two curves A and B, the shouldering torque T_(s) is equal toabout 70% of the optimum makeup torque specified for this type ofthreaded connection because of the particular pairing of the threadedelements tested (high interferences both between the threadings andbetween the sealing surfaces).

Curves A and B in FIG. 20 show, for VAM TOP® threaded connectionssimilar to those of the preceding figure and treated in the same manner,the variation in the shouldering torque as a function of the number ofcycles of makeup-breakout carried out (up to 10 cycles), the shoulderingtorque being expressed by a relative value with respect to the optimummakeup torque, this latter being an average value between the minimummakeup torque and the maximum torque specified.

FIG. 20 shows that the shouldering torque varies little during these 10makeup-breakout cycles and that the stability of the shouldering torqueis better for a threaded connection of the invention (curve A) than fora connection coated with API grease (curve B) even when the coating isrenewed between makeup-breakout cycles: the shouldering torque T_(S)varies from 69% of the optimum makeup torque on the 1^(st) makeup to 58%on the 10^(th) makeup in the case of curve A compared to 70% on the 1stmakeup and 36% on the 6th makeup in the case of curve B. This shows thatsufficient lubricating substance remains on a threaded connection of theinvention to obtain stable lubricating characteristics both in thethreads and in the bearing surfaces after 10 makeup-breakout cycles.

Curves C and D in FIG. 20 show for respectively the same threadedconnections as those for curves A and B of FIG. 20, the variation in theinitial breakout torque as a function of the number of breakouts for 10consecutive makeup-breakout cycles, this variation being expressed withrespect to the final makeup torque.

The first teaching provided by curve C in FIG. 20 (threaded connectionof the invention) is that, because of the absence of galling, theconnection can always be broken out.

The initial breakout torque varies for curve C between 97% and 106% ofthe final makeup torque, again showing stable performances.

In the case of curve D of FIG. 20 (API grease), the initial breakouttorque varies between 84% and 101% of the final makeup torque, giving aslightly greater variation than with curve C.

The final visual appearance of the threads and sealing surfaces after 10makeup-breakout cycles is excellent, with no trace of galling.

The table below compares the number of makeup-breakout cycles obtainedbefore the appearance of galling for a maximum of 10 cycles carried outon the same type of VAM TOP® 5½″ 17 lb/ft grade L80 threaded connectionsas for the tests of FIGS. 19 and 20, but the threaded elements areselected to have low interference between the threadings and highinterference between the bearing surfaces.

Number of cycles before galling threaded connection with API 5A2 grease≧10 (reference) threaded connection with dry MoS₂ varnish 6 threadedconnection of present invention with ≧10 lubricating substance accordingto Example 2

The results confirm that the application of a prior art MoS₂ dry varnishrapidly leads to unacceptable galling, while that of the lubricatingsubstance defined above produces satisfactory results comparable, fromthe point of view of galling, with the results obtained with connectionscoated with API grease.

1. A male or female threaded element for a threaded tubular connection,comprising: a respective male or female threading; and a lubricatingsubstance deposited prior to make-up of the threaded tubular connectionas a thin layer of less than 0.1 mm on at least a surface of threads ofthe threading, wherein the lubricating substance is a homogeneeusmixture of: a) a thickening agent, b) at least one extreme pressureadditive, and c) an oil, wherein said at least one extreme pressureadditive is a chemical EP additive, and wherein said chemical EPadditive is capable of use at Hertz pressures of 1000 MPa or more. 2.The threaded element according to claim 1, wherein the chemical EPadditive and the thickening agent are soluble in the oil.
 3. Thethreaded element according to claim 1, wherein the thickening agentcontains chemical molecules of a marked polar nature.
 4. The threadedelement according to claim 1, wherein the thickening agent is chemicallystable up to a temperature of 120° C. or more.
 5. The threaded elementaccording to claim 1, wherein the thickening agent is an organicthickening agent.
 6. The threaded element according to claim 1, whereinthe thickening agent is a mineral thickening agent.
 7. The threadedelement according to claim 1, wherein the chemical EP additive isselected from the group consisting of sulfur EP additive, asulfur-containing chemical EP additive, a phosphorus-containingadditive, a sulfur and phosphorus-containing additive, achlorine-containing EP additive, a modified ester-containing additive, anon modified ester-containing additive, a modified fatty acid-containingadditive and a complex ester-containing additive.
 8. The threadedelement according to claim 1, wherein the thickening agent is anoxidized petrolatum wax, wherein a plurality of chemical EP additives ispresent, comprising a sulfur-containing product, an overbased suiphonateand a metallic dithiophosphate, and wherein the oil is a mineral oil. 9.The threaded element according to claim 1, wherein the lubricatingsubstance comprises at least one EP additive with a physical action inthe form of solid sub-micronic particles.
 10. The threaded elementaccording to claim 1, wherein the at least one EP additive hasanti-corrosion properties.
 11. The threaded element according to claim1, wherein the total content of EP additives in the lubricatingsubstance is in the range 5% to 50% by weight, and wherein the EPadditives include a plurality of chemical EP additives.
 12. The threadedelement according to claim 11, wherein the content of thickening agentin the lubricating substance is in the range 5% to 60% by weight, andwherein the content of oil in the lubricating substance is in the range30% to 75% by weight.
 13. The threaded element according to claim 11,wherein the content of thickening agent in the lubricating substance isin the range 60% to 80% by weight, and wherein the content of oil in thelubricating substance is in the range 5% to 20% by weight.
 14. Thethreaded element according to claim 1, wherein the chemical EP additivecomprises a chlorinated paraffin, the content of thickening agent in thelubricating substance is in the range 25% to 60% by weight, wherein thetotal content of EP additives in the lubricating substance is in therange 40% to 75% by weight, and wherein the content of oil in thelubricating substance is in the range 0.5% to 15% by weight.
 15. Thethreaded element according to claim 1, wherein the weight of the layerof lubricating substance is in the range 0.1 g/m² to 40 g/m².
 16. Thethreaded element according to claim 1, wherein said surface of thethreads is treated to adsorb or absorb the lubricating substance and isthe surface of a layer selected from the group consisting ofphosphatation layers, oxalation layers and metallic layers.
 17. Thethreaded element according to claim 1, wherein the surface of thethreads is treated to endow said surface with a controlled roughness soas to adsorb or absorb the lubricating substance.
 18. The threadedelement according claim 16, wherein the surface of the threads istreated to adsorb or absorb the lubricating substance over a depth inthe range 0.003 mm to 0.080 mm.
 19. The threaded element according toclaim 1, wherein the threaded element further comprises at least onesealing surface, the lubricating substance being also deposited as athin layer on said sealing surface.
 20. The threaded element accordingto claim 1, wherein the threaded element further comprises at least onemakeup abutment, the lubricating substance being also deposited as athin layer on each surface of the abutment.
 21. The threaded elementaccording to claim 19, wherein all of the surfaces on which thelubricating substance is deposited as a thin layer are surfaces that aretreated to adsorb or absorb the lubricating substance.
 22. The threadedelement according to claim 1, wherein the lubricating substancecomprises less than 5% by weight of a colorant that is inactive withrespect to galling-resistant properties of the tubular connection.
 23. Athreaded tubular connection comprising a male threaded element and afemale threaded element, each of said threaded elements comprising acorresponding threading, said threadings being made up one into theother to a connected position, wherein at least one of the two threadedelements is a threaded element according to claim
 1. 24. The threadedtubular connection according to claim 23, wherein both threaded elementsare elements according to claim 1, and only one of the threaded elementhas a surface treated to adsorb or absorb said lubricating substance.25. A method for preparing a threaded tubular connection between a malethreading and a female threading, the method comprising the steps of a)preparing a homogeneous liquid mixture comprising a volatile solvent; athickening agent; at least one extreme pressure additive and an oil; b)prior to making-up said tubular connection, applying a thin layer ofsaid liquid mixture of substantially uniform thickness to a surface ofthreads of at least one of said male and female threadings; and c)evaporating the volatile solvent thereby obtaining prior to make-up athin layer of less than 0.1 mm of a lubricating substance on saidsurface of said threads, wherein said at least one extreme pressureadditive is a chemical EP additive, and wherein said chemical EPadditive is capable of use at Hertz measures of 1000 MPa or more. 26.The threaded element according to claim 4, wherein the thickening agentis chemically stable up to a temperature of 160° C. or more.
 27. Thethreaded element according to claim 11, wherein the total content of EPadditives in the lubricating substance is in the range of from 15% to32% by weight.
 28. The threaded element according to claim 12, whereinthe content of thickening agent in the lubricating substance is in therange of from 8% to 40% by weight.
 29. The method of claim 25, furthercomprising the step of treating said surface of the threads to absorb oradsorb the lubricating substance prior to said step of applying saidthin layer of said liquid mixture.
 30. The threaded element according toclaim 1, wherein said surface is treated to adsorb or absorb saidlubricating substance.
 31. The threaded element according to claim 1,wherein proportions of constituents of the lubricating substance areselected so that said lubricating substance has a consistency thatensures a self-fed lubrication regime and a film-forming nature.
 32. Thethreaded element according to claim 1, wherein said lubricatingsubstance is free of any non-chemical EP additive.
 33. The threadedelement according to claim 1, wherein said lubricating substance is freeof any heavy metals.
 34. The threaded element according to claim 33,wherein said lubricating substance is free of any toxic compound of saidheavy metals.
 35. The threaded element according to claim 33, whereinsaid lubricating substance is free of Zn.
 36. The threaded elementaccording to claim 33, wherein said lubricating substance is free of Cu.37. The threaded element according to claim 33, wherein said lubricatingsubstance is free of Pb.
 38. The threaded element according to claim 1,wherein said lubricating substance comprises three different chemical EPadditives.
 39. The threaded element according to claim 38, wherein saidlubricating substance consists essentially of said thickening agent,said three chemical EP additives and said oil.
 40. The threaded elementaccording to claim 38, wherein said three different chemical EPadditives are a sulfur-containing product, a sulphonate, and adithiophosphate.
 41. The threaded element according to claim 39, whereinsaid lubricating substance is free of any additional substance affectingthe galling-resistant properties of the tubular connection.
 42. Thethreaded tubular connection according to claim 23, wherein saidconnection is resistant to galling.
 43. The method according to claim25, wherein said step of applying said thin layer of said liquid mixturecomprises spraying said liquid mixture over said surface of threadsprior to make-up.